In the prior art, it is known that the position and motion of aircraft in an airspace can be periodically detected and measured by an active or passive detection and ranging system. The ranging system sends the periodically obtained information in the form of coded signals to a processor and an associated interactive interface. In turn, the processor causes the signals to be transformed and displayed at the interface. The interface may include a surface such as a polychromatic cathode ray tube upon which the aircraft position information is shown, means coupling the processor for varying the display, means for controlling the detection and ranging system, and means for communicating with aircraft. Such a system, although frequently sited on the ground, may likewise be air or seaborne.
Typifying the prior art patent literature are:
(1) Buchanan et al, U.S. Pat. No. 4,196,474, "Information Display Method and Apparatus for Air Traffic Control", issued Apr. 1, 1980. PA1 (2) Corcoran, U.S. Pat. No. 4,023,158, "Real Three-dimension Visual Display Arrangement", issued May 10, 1977. PA1 (3) Hammack, U.S. Pat. No. 3,996,950, "Method and Apparatus for Automatically Detecting and Tracking Moving Objects and Similar Applications", issued Dec. 7, 1976. PA1 (4) Levine, U.S. Pat. No. 3,971,025, "Airport Ground Surveillance System with Aircraft Taxi Control Feature", issued July 20, 1976. PA1 (5) Gilbert et al, U.S. Pat. No. 3,925,750, "Air Traffic Control System", issued Dec. 9, 1975. PA1 (6) Inselberg et al, "Intelligent Instrumentation and Process Control", Proceedings of the Second Conference on AI Applications, IEEE, Dec. 11-13, 1985, pp. 302-307, and references cited therein. PA1 (a) interior points (points in N-space) to a hypersurface represent the acceptable states of a system model, PA1 (b) control requires staying within the interior of said surface, and PA1 (c) a current abbreviated description of the system state, i.e., display, involves the mapping of points in N-space into convenient 2-dimensional form.
These references describe systems and methods for providing the near real-time isometric display of state variable data (aircraft identity, position, velocity) in two and three dimensions. However, significant dimensional information may be lost. For instance, a 2-dimensional radar display may show position (range) but no height data. Alternatively, position information may be shown in polar coordinates dimensionally graphed, but other information such as height and ground speed may appear only as numerical tags to the display blip.
Notwithstanding, recent years have witnessed a crowding of the skies around air traffic control (ATC) sites with increasing numbers of both scheduled and nonscheduled aircraft seeking entrance or exit from or to designated airspace and ground facilities. One consequence is the crowding of information appearing at the counterpart ATC displays. This means that ATC personnel and others utilizing the displays may overlook data present, not notice data absent, and otherwise misinterpret the system state. This becomes critical where the displayed data concerns potential collisions involving closing distances and velocities among aircraft. Parenthetically, Gilbert, in FIG. 6, exhibits a typical crowded airborne ATC display.
Another source of prior art relates to a theory of optimal control systems using N-dimensional geometry. This is taught by:
According to Inselberg, an N-dimensional/coordinate geometry may be used to characterise N mensurable attributes of each object in a system. Relatedly, process control consists of maintaining some relations defined on those attributes invariant and others constrained. Optimal process control is one in which:
Inselberg proposes that the N-dimensional to 2-dimensional mapping for a display be in the form of N axes parallel, say, to the y-axis in the xy-plane. Each point in the higher dimension can have its N coordinates (c1, c2, c3, . . . , cN) depicted as a polygonal line in the xy-plane. At page 305, he points out that a general convex hypersurface in N-dimensions can be represented by the "envelope" of the set of polygonal lines. This is analogous to the 2- or 3-dimensional space of defining a curve as the "envelope" of its tangents, and defining a surface as the "envelope" of its tangent planes. Reference also can be made to Edna E. Kramer, "The Nature and Growth of Modern Mathematics", Princeton University Press, copyright 1981, page 160; and Aleksandrov et al, "Mathematics, Its Content, Method, and Meaning", MIT Press, copyright 1963, Vol 2, pp. 108-110.
The Inselberg article further points out several properties of this hypersurface envelope as mapped onto the xy-plane. First, a "feasible point" satisfying control requirements is interior to the hypersurface. Second, the relation between adjacent ones of the N-parallel axes is defined by the envelope shape. Third, the envelope shape is dependent upon the order in which the axes appear. Lastly, varying the order permits a way of finding and displaying these "feasible points".